The proposed research involves the study of both behavioral and averaged evoked potential (AEP) responses during perception of auditory patterns, with the goal of defining the underlying psychophysiological mechanisms. Stimulus patterns will be three temporally spaced tone or noise bursts involving two frequencies ("high" and "low") or two intensities ("loud" and "soft"). The finding that normal subjects often reverse acoustic cues in auditory pattern discrimination will be used as an investigative tool in the AEP part of the project. (In acoustic reversals "loud" is substituted for "soft" and vice versa in Intensity Patterns and "high" is substituted for "low" and vice versa in Frequency Patterns.) This approach for gathering information about the basic processes in auditory pattern perception in normal young adult subjects will consist of the study of spectral analyses of the EEG and early and late components of the AEP's associated with three classes of behavioral responses (correct, reversed, and combined-errors) to the same stimulus patterns. Investigation of these electrophysiological aspects of the stimulus-response relationship may determine pre- or post-stimulus EEG correlates which would allow prediction of the accuracy of the response prior to complete presentation of the pattern. Parallel behavioral studies of auditory pattern perception will document its development in normal young children. Then, it will be related to delayed language development and learning disabilities in groups of children with these disorders. Performance of patients with hemispheric lesions should contribute further information about the cerebral mechanisms involved in auditory pattern perception so that useful diagnostic procedures may be developed.